The purpose of this project is to establish a predictable model of hereditary cataract in deer mice (Peromyscus maniculatus) which resembles senile cataract in humans. The cataract is inherited as an autosomal recessive. The value of this model lies in the late onset of cataract after development of a clear lens, the predictability of cataract from a phenotypic marker (fused toes), and the resemblance of the Peromyscus cataract, histologically, to several varieties of human senile cataract, the cortical, posterior subcapsular, and the hypermature cataract. A small colony of Peromyscus is available, but further breeding efforts are necessary in order to obtain sufficient animals to characterize the colony and the cataract metabolically and genetically. Biomicroscopic study of the lenses of all animals will be conducted, followed by definitive light and electron microscopy of selected lenses. General health and disease characteristics will be studied by blood and urine analyses and autopsy of old, non-breeding animals. When sufficient pre-cataractous mice are available, and the time of onset of cataracts is established, autoradiographic and biochemical studies will be undertaken aimed at detecting differences in DNA, RNA and protein metabolism in the normal versus the early cataractous lenses. Chromosomes will be studied using giemsa and quinacrine mustard banding techniques, and genetic linkage studies will be initiated.